Node Web Audio API

Node.js bindings for the Rust implementation of the Web Audio API.

This library aims to provide an implementation that is both efficient and compliant with the specification.

• see orottier/web-audio-api-rs for the "real" audio guts
• use napi-rs for the Node.js bindings

For library authors who which to write components that run both in Node.js and the browser, we also provide isomorphic-web-audio-api

Install

npm install [--save] node-web-audio-api

Example Use

import { AudioContext, OscillatorNode, GainNode } from 'node-web-audio-api';
// or using old fashioned commonjs syntax:
// const { AudioContext, OscillatorNode, GainNode } = require('node-web-audio-api');
const audioContext = new AudioContext();

setInterval(() => {
  const now = audioContext.currentTime;
  const frequency = 200 + Math.random() * 2800;

  const env = new GainNode(audioContext, { gain: 0 });
  env.connect(audioContext.destination);
  env.gain
    .setValueAtTime(0, now)
    .linearRampToValueAtTime(0.2, now + 0.02)
    .exponentialRampToValueAtTime(0.0001, now + 1);

  const osc = new OscillatorNode(audioContext, { frequency });
  osc.connect(env);
  osc.start(now);
  osc.stop(now + 1);
}, 80);

Running the Examples

To run all examples locally on your machine you will need to:

1. Install Rust toolchain

curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh

2. Clone the repo and build the binary on your machine

git clone https://github.com/ircam-ismm/node-web-audio-api.git
cd node-web-audio-api
npm install
npm run build

3. Run the examples from the project's root directory

node examples/granular-scrub.js

Caveats

• AudioBuffer#getChannelData is implemented but not reliable in some situations. Your should prefer AudioBuffer#copyToChannel and AudioBuffer#copyFromChannel when you want to access or manipulate the underlying samples in a safe way.
• Streams: only a minimal audio input stream and the MediaStreamSourceNode are provided. All other MediaStream features are left on the side for now as they principally concern a different API specification, which is not a trivial problem.

Supported Platforms - Prebuilt Binaries

We provide prebuilt binaries for the following platforms:

Important notes

• If you need support for another platform, please fill an issue and we will see what we can do.

• All provided Linux binaries are built with the jack flag, which should work either with properly configured Jack or pipewire-jack backends. If this is a limitation for you, please fill an issue and we will see what we can do.

Manual Build

If prebuilt binaries are not shippped for your platform, you will need to:

1. Install the Rust toolchain

curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh

2. Install and build from github

git clone https://github.com/ircam-ismm/node-web-audio-api.git node_modules/node-web-audio-api
cd node_modules/node-web-audio-api
npm install
npm run build

The package will be built on your machine, which might take some time.

Be aware that the package won't be listed on your package.json file, and that it won't be re-installed if running npm install again. A possible workaround would be to include the above in a postinstall script.

Notes for Linux users

Build

To build the library, you will need to manually install the libasound2-dev package:

sudo apt install libasound2-dev

Optionally, if you use the Jack Audio Backend, the libjack-jackd2-dev package:

sudo apt install libjack-jackd2-dev

In such case, you can use the npm run build:jack script to enable the Jack feature.

Audio backend and latency

Using the library on Linux with the ALSA backend might lead to unexpected cranky sound with the default render size (i.e. 128 frames). In such cases, a simple workaround is to pass the playback latency hint when creating the audio context, which will increase the render size to 1024 frames:

const audioContext = new AudioContext({ latencyHint: 'playback' });

For real-time and interactive applications where low latency is crucial, you should instead rely on the JACK backend provided by cpal. By default the audio context will use that backend if a running JACK server is found.

If you don't have JACK installed, you can still pass the WEB_AUDIO_LATENCY=playback environment variable to all examples to create the audio context with the playback latency hint, e.g.:

WEB_AUDIO_LATENCY=playback node examples/amplitude-modulation.mjs

Development notes

Synchronize versioning

The npm postversion script rely on cargo-bump to maintain versions synced between the package.json and the Cargo.toml files. Therefore, you will need to install cargo-bump on your machine

cargo install cargo-bump

Running the web-platform-test suite

Follow the steps for 'Manual Build' first. Then checkout the web-platform-tests submodule with:

git submodule init
git submodule update

Then run:

npm run wpt                      # build in debug mode and run all wpt test
npm run wpt:only                 # run all wpt test without build
npm run wpt -- --list            # list all wpt test files
npm run wpt -- --filter <string> # apply <string> filter on executed/listed wpt tests

License

BSD-3-Clause